1. Field of the Invention
The present invention relates to a gas compressor that rotates two rotors to suck, compress, and discharge gas.
2. Description of the Related Art
There has been conventionally known a gas compressor having two rotary rotors housed in a housing (e.g., JP-A-2005-220785). In this gas compressor, one end of the rotary shaft of each of the rotors is supported by a bearing hole of one housing head and the other end thereof is supported by a bearing hole of the housing.
To increase the discharge pressure of the gas compressor to high pressure, it is necessary to reduce a clearance between the rotors and the housing and to improve compression efficiency. In particular, in a gas compressor that does not use oil for improving seal performance between the rotors and the housing, it is greatly necessary to decrease the clearance. For this reason, the relative position of the housing to the housing head is usually determined by the use of positioning pins to improve the coaxial degree to which the bearing hole of the housing is coaxial with the bearing hole of the housing head, thereby the clearance between the rotors and the housing is decreased.
However, in the foregoing compressor, the accuracies with which pin holes are formed in the housing head and the housing are added to the accuracy of the coaxial degree to which the housing head is coaxial with the housing. Thus, the accuracy with which the housing head is coaxial with the housing deteriorates. Further, because bearing holes corresponding to the rotary shafts of the two rotors are formed in one housing head, the accuracies with which the respective bearing holes are formed are effected to the coaxial degree of the two bearing holes formed in the housing head. Thus, this presents a problem that the clearance between the rotors and the housing becomes large.
Moreover, because the pin holes need to be formed in the housing and the housing head with high accuracy, there is presented a problem that manufacturing cost increases. Further, when the housing head is positioned with respect to the housing by the use of a positioning pin, it takes much time to combine the housing head with the housing. This presents a problem that steps required to combine the housing head with the housing increase.